1perf-stat(1) 2============ 3 4NAME 5---- 6perf-stat - Run a command and gather performance counter statistics 7 8SYNOPSIS 9-------- 10[verse] 11'perf stat' [-e <EVENT> | --event=EVENT] [-a] <command> 12'perf stat' [-e <EVENT> | --event=EVENT] [-a] -- <command> [<options>] 13'perf stat' [-e <EVENT> | --event=EVENT] [-a] record [-o file] -- <command> [<options>] 14'perf stat' report [-i file] 15 16DESCRIPTION 17----------- 18This command runs a command and gathers performance counter statistics 19from it. 20 21 22OPTIONS 23------- 24<command>...:: 25 Any command you can specify in a shell. 26 27record:: 28 See STAT RECORD. 29 30report:: 31 See STAT REPORT. 32 33-e:: 34--event=:: 35 Select the PMU event. Selection can be: 36 37 - a symbolic event name (use 'perf list' to list all events) 38 39 - a raw PMU event (eventsel+umask) in the form of rNNN where NNN is a 40 hexadecimal event descriptor. 41 42 - a symbolically formed event like 'pmu/param1=0x3,param2/' where 43 param1 and param2 are defined as formats for the PMU in 44 /sys/bus/event_source/devices/<pmu>/format/* 45 46 - a symbolically formed event like 'pmu/config=M,config1=N,config2=K/' 47 where M, N, K are numbers (in decimal, hex, octal format). 48 Acceptable values for each of 'config', 'config1' and 'config2' 49 parameters are defined by corresponding entries in 50 /sys/bus/event_source/devices/<pmu>/format/* 51 52 Note that the last two syntaxes support prefix and glob matching in 53 the PMU name to simplify creation of events accross multiple instances 54 of the same type of PMU in large systems (e.g. memory controller PMUs). 55 Multiple PMU instances are typical for uncore PMUs, so the prefix 56 'uncore_' is also ignored when performing this match. 57 58 59-i:: 60--no-inherit:: 61 child tasks do not inherit counters 62-p:: 63--pid=<pid>:: 64 stat events on existing process id (comma separated list) 65 66-t:: 67--tid=<tid>:: 68 stat events on existing thread id (comma separated list) 69 70 71-a:: 72--all-cpus:: 73 system-wide collection from all CPUs (default if no target is specified) 74 75-c:: 76--scale:: 77 scale/normalize counter values 78 79-d:: 80--detailed:: 81 print more detailed statistics, can be specified up to 3 times 82 83 -d: detailed events, L1 and LLC data cache 84 -d -d: more detailed events, dTLB and iTLB events 85 -d -d -d: very detailed events, adding prefetch events 86 87-r:: 88--repeat=<n>:: 89 repeat command and print average + stddev (max: 100). 0 means forever. 90 91-B:: 92--big-num:: 93 print large numbers with thousands' separators according to locale 94 95-C:: 96--cpu=:: 97Count only on the list of CPUs provided. Multiple CPUs can be provided as a 98comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2. 99In per-thread mode, this option is ignored. The -a option is still necessary 100to activate system-wide monitoring. Default is to count on all CPUs. 101 102-A:: 103--no-aggr:: 104Do not aggregate counts across all monitored CPUs. 105 106-n:: 107--null:: 108 null run - don't start any counters 109 110-v:: 111--verbose:: 112 be more verbose (show counter open errors, etc) 113 114-x SEP:: 115--field-separator SEP:: 116print counts using a CSV-style output to make it easy to import directly into 117spreadsheets. Columns are separated by the string specified in SEP. 118 119-G name:: 120--cgroup name:: 121monitor only in the container (cgroup) called "name". This option is available only 122in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to 123container "name" are monitored when they run on the monitored CPUs. Multiple cgroups 124can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup 125to first event, second cgroup to second event and so on. It is possible to provide 126an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have 127corresponding events, i.e., they always refer to events defined earlier on the command 128line. If the user wants to track multiple events for a specific cgroup, the user can 129use '-e e1 -e e2 -G foo,foo' or just use '-e e1 -e e2 -G foo'. 130 131If wanting to monitor, say, 'cycles' for a cgroup and also for system wide, this 132command line can be used: 'perf stat -e cycles -G cgroup_name -a -e cycles'. 133 134-o file:: 135--output file:: 136Print the output into the designated file. 137 138--append:: 139Append to the output file designated with the -o option. Ignored if -o is not specified. 140 141--log-fd:: 142 143Log output to fd, instead of stderr. Complementary to --output, and mutually exclusive 144with it. --append may be used here. Examples: 145 3>results perf stat --log-fd 3 -- $cmd 146 3>>results perf stat --log-fd 3 --append -- $cmd 147 148--pre:: 149--post:: 150 Pre and post measurement hooks, e.g.: 151 152perf stat --repeat 10 --null --sync --pre 'make -s O=defconfig-build/clean' -- make -s -j64 O=defconfig-build/ bzImage 153 154-I msecs:: 155--interval-print msecs:: 156Print count deltas every N milliseconds (minimum: 10ms) 157The overhead percentage could be high in some cases, for instance with small, sub 100ms intervals. Use with caution. 158 example: 'perf stat -I 1000 -e cycles -a sleep 5' 159 160--interval-count times:: 161Print count deltas for fixed number of times. 162This option should be used together with "-I" option. 163 example: 'perf stat -I 1000 --interval-count 2 -e cycles -a' 164 165--timeout msecs:: 166Stop the 'perf stat' session and print count deltas after N milliseconds (minimum: 10 ms). 167This option is not supported with the "-I" option. 168 example: 'perf stat --time 2000 -e cycles -a' 169 170--metric-only:: 171Only print computed metrics. Print them in a single line. 172Don't show any raw values. Not supported with --per-thread. 173 174--per-socket:: 175Aggregate counts per processor socket for system-wide mode measurements. This 176is a useful mode to detect imbalance between sockets. To enable this mode, 177use --per-socket in addition to -a. (system-wide). The output includes the 178socket number and the number of online processors on that socket. This is 179useful to gauge the amount of aggregation. 180 181--per-core:: 182Aggregate counts per physical processor for system-wide mode measurements. This 183is a useful mode to detect imbalance between physical cores. To enable this mode, 184use --per-core in addition to -a. (system-wide). The output includes the 185core number and the number of online logical processors on that physical processor. 186 187--per-thread:: 188Aggregate counts per monitored threads, when monitoring threads (-t option) 189or processes (-p option). 190 191-D msecs:: 192--delay msecs:: 193After starting the program, wait msecs before measuring. This is useful to 194filter out the startup phase of the program, which is often very different. 195 196-T:: 197--transaction:: 198 199Print statistics of transactional execution if supported. 200 201STAT RECORD 202----------- 203Stores stat data into perf data file. 204 205-o file:: 206--output file:: 207Output file name. 208 209STAT REPORT 210----------- 211Reads and reports stat data from perf data file. 212 213-i file:: 214--input file:: 215Input file name. 216 217--per-socket:: 218Aggregate counts per processor socket for system-wide mode measurements. 219 220--per-core:: 221Aggregate counts per physical processor for system-wide mode measurements. 222 223-M:: 224--metrics:: 225Print metrics or metricgroups specified in a comma separated list. 226For a group all metrics from the group are added. 227The events from the metrics are automatically measured. 228See perf list output for the possble metrics and metricgroups. 229 230-A:: 231--no-aggr:: 232Do not aggregate counts across all monitored CPUs. 233 234--topdown:: 235Print top down level 1 metrics if supported by the CPU. This allows to 236determine bottle necks in the CPU pipeline for CPU bound workloads, 237by breaking the cycles consumed down into frontend bound, backend bound, 238bad speculation and retiring. 239 240Frontend bound means that the CPU cannot fetch and decode instructions fast 241enough. Backend bound means that computation or memory access is the bottle 242neck. Bad Speculation means that the CPU wasted cycles due to branch 243mispredictions and similar issues. Retiring means that the CPU computed without 244an apparently bottleneck. The bottleneck is only the real bottleneck 245if the workload is actually bound by the CPU and not by something else. 246 247For best results it is usually a good idea to use it with interval 248mode like -I 1000, as the bottleneck of workloads can change often. 249 250The top down metrics are collected per core instead of per 251CPU thread. Per core mode is automatically enabled 252and -a (global monitoring) is needed, requiring root rights or 253perf.perf_event_paranoid=-1. 254 255Topdown uses the full Performance Monitoring Unit, and needs 256disabling of the NMI watchdog (as root): 257echo 0 > /proc/sys/kernel/nmi_watchdog 258for best results. Otherwise the bottlenecks may be inconsistent 259on workload with changing phases. 260 261This enables --metric-only, unless overriden with --no-metric-only. 262 263To interpret the results it is usually needed to know on which 264CPUs the workload runs on. If needed the CPUs can be forced using 265taskset. 266 267--no-merge:: 268Do not merge results from same PMUs. 269 270When multiple events are created from a single event specification, 271stat will, by default, aggregate the event counts and show the result 272in a single row. This option disables that behavior and shows 273the individual events and counts. 274 275Multiple events are created from a single event specification when: 2761. Prefix or glob matching is used for the PMU name. 2772. Aliases, which are listed immediately after the Kernel PMU events 278 by perf list, are used. 279 280--smi-cost:: 281Measure SMI cost if msr/aperf/ and msr/smi/ events are supported. 282 283During the measurement, the /sys/device/cpu/freeze_on_smi will be set to 284freeze core counters on SMI. 285The aperf counter will not be effected by the setting. 286The cost of SMI can be measured by (aperf - unhalted core cycles). 287 288In practice, the percentages of SMI cycles is very useful for performance 289oriented analysis. --metric_only will be applied by default. 290The output is SMI cycles%, equals to (aperf - unhalted core cycles) / aperf 291 292Users who wants to get the actual value can apply --no-metric-only. 293 294EXAMPLES 295-------- 296 297$ perf stat -- make -j 298 299 Performance counter stats for 'make -j': 300 301 8117.370256 task clock ticks # 11.281 CPU utilization factor 302 678 context switches # 0.000 M/sec 303 133 CPU migrations # 0.000 M/sec 304 235724 pagefaults # 0.029 M/sec 305 24821162526 CPU cycles # 3057.784 M/sec 306 18687303457 instructions # 2302.138 M/sec 307 172158895 cache references # 21.209 M/sec 308 27075259 cache misses # 3.335 M/sec 309 310 Wall-clock time elapsed: 719.554352 msecs 311 312CSV FORMAT 313---------- 314 315With -x, perf stat is able to output a not-quite-CSV format output 316Commas in the output are not put into "". To make it easy to parse 317it is recommended to use a different character like -x \; 318 319The fields are in this order: 320 321 - optional usec time stamp in fractions of second (with -I xxx) 322 - optional CPU, core, or socket identifier 323 - optional number of logical CPUs aggregated 324 - counter value 325 - unit of the counter value or empty 326 - event name 327 - run time of counter 328 - percentage of measurement time the counter was running 329 - optional variance if multiple values are collected with -r 330 - optional metric value 331 - optional unit of metric 332 333Additional metrics may be printed with all earlier fields being empty. 334 335SEE ALSO 336-------- 337linkperf:perf-top[1], linkperf:perf-list[1] 338